1. Field of the Invention
The present invention pertains to a flat bottom plastic bag which is formed from an extruded or blown film tubular plastic sleeve and to an improved process of making such a bag on a continuous or intermittent basis.
2. Background
In the art of plastic bags there have been previous efforts to develop a bag which when opened is adapted to form a flat bottom and is substantially freestanding. Such characteristics of a bag or sack are particularly desired in the grocery industry and other applications wherein it is desired to fill the bag with several articles which preferably are kept upright and/or are stacked for more efficient utilization of the bag's capacity. A problem of longstanding with lightweight plastic bags formed of plastic film such as polyethylene or polypropylene is the effective formation of folds and webs or gussets in the bag which will provide a flat bottom which may be formed by a somewhat snap opening action such as may be accomplished with flat bottom paper bags. Prior art efforts to develop flat bottom plastic bags which can be economically manufactured on a substantially continuous basis have not been highly successful and the bags so manufactured do not have the desired opening and freestanding characteristics.
However, in accordance with the present invention several deficiencies associated with prior art plastic film type bags have been overcome in providing a bag which may be opened to form a substantially flat rectangular bottom wall and wherein the bag sidewalls are freestanding, both characteristics being highly desired in bags which are used for grocery and other mixed commodity usage.